One method of printing used in an image forming apparatus such as a printer, photocopier, or the like is an intermediate transfer method.
In an intermediate transfer method, for example in the case of color printing, as illustrated in FIG. 4, a toner image on photosensitive drums 101 corresponding to the colors black, yellow, magenta, cyan, and the like undergoes primary transfer to the surface of an endless intermediate transfer belt 102. The toner image (color image) on the intermediate transfer belt 102 then undergoes secondary transfer to a recording medium 103, such as paper. The toner image (color image) on the recording medium is fixed to the recording medium by a fixer 104. In FIG. 4, reference numeral 105 indicates a secondary transfer roller, and reference numeral 106 indicates a roller.
As the intermediate transfer belt, a conductive endless belt 1 with a multilayer structure, including a base layer 2 that is the belt body and a surface layer 3 on the base layer 2, is generally used. An example is shown in FIG. 1.
The toner image on the photosensitive drum undergoes primary transfer to the surface layer of the conductive endless belt and then undergoes secondary transfer from this surface layer onto the recording medium.
Accordingly, the conductive endless belt has the function of subjecting the toner image, which underwent primary transfer from the photosensitive drum, to secondary transfer to the recording medium. Therefore, the conductive endless belt is required to have the property of the toner image being transferred to the recording medium at the time of secondary transfer without remaining on the conductive endless belt, i.e. the conductive endless belt is required to have toner releasability.
If the toner releasability of the conductive endless belt is low, then the toner image that undergoes secondary transfer onto the recording medium may be insufficient, leading to a reduction in printing quality. Furthermore, if the toner releasability is low, the toner that remains on the conductive endless belt becomes waste toner, which lowers the usage efficiency of materials. This is undesirable in terms of saving resources.
Regarding conductive endless belts, for example in order to improve the transfer efficiency when transferring an image from the intermediate transfer belt to the recording medium, JP 2009-192901 A (PTL 1) discloses using, on the surface layer of the conductive endless belt used as the intermediate transfer belt, a hard coat layer that has a particular pencil hardness and contact angle.